Contents
What is Tweedie variance power?
Tweedie distributions are a family of distributions that include gamma, normal, Poisson and their combinations. This distribution is especially useful for modeling positive continuous variables with exact zeros. The variance of the Tweedie distribution is proportional to the p-th power of the mean var(yi)=ϕμpi.
What is Tweedie power?
Tweedie random variables are exponential dispersion models that have power unit variance functions, are infinitely divisible, and are closed under translations and scale transformations. Notably, a Tweedie random variable has an indexing/power param- eter that is key in describing its distribution.
When to use Tweedie?
Tweedie distribution is a special case of exponential dispersion models and is often used as a distribution for generalized linear models. It can have a cluster of data items at zero and this particular property makes it useful for modeling claims in the insurance industry.
What is Tweedie GLM?
The Tweedie package allows you to fit a glm with any power function and any power link. In the glm family call, var. power is the α parameter so that var.
What is Gamma Poisson?
The Gamma–Poisson distribution is a two-stage model for the distribution of a discrete variable, e.g., the counts of micro-organisms. To fit a Gamma–Poisson model to observed data requires that we are able to differentiate between variation at the two levels.
What is Poisson loss?
The Poisson loss is the mean of the elements of the Tensor y_pred – y_true * log(y_pred) .
Is there such a thing as a Tweedie GLM?
There are no theoretical Tweedie GLMs with var.power between 0 and 1 (Jorgensen 1987). The tweedie function will work for those values but the family should be interpreted in a quasi-likelihood sense. Theoretical Tweedie GLMs do exist for negative values of var.power, but they are of little practical application.
How to fit a GLM to a power function?
The Tweedie package allows you to fit a glm with any power function and any power link. In the glm family call, var.power is the α parameter so that var.power=1.1 specifies α = 1.1 . The var.power refers to exponent of the glm variance function, so that var.power=0 specifies a normal family, var.power=1 means Poisson family,…
When to use a Tweedie generalized linear model?
The most interesting Tweedie families occur for var.power between 1 and 2. For these GLMs, the response distribution has mass at zero (i.e., it has exact zeros) but is otherwise continuous on the positive real numbers (Smyth, 1996; Hasan et al, 2012). These GLMs have been used to model rainfall for example.
Are there any negative values of the Tweedie function?
Theoretical Tweedie GLMs do exist for negative values of var.power, but they are of little practical application. These distributions assume The tweedie function will work for those values but the family should be interpreted in a quasi-likelihood sense.